When a double glazed pane cracks or breaks, the whole sealed unit is replaced, not just the single sheet of glass. We make the opening safe first – with boarding or temporary glazing if needed – then measure, order a new unit made to size and fit it into your existing uPVC, aluminium or composite frame. Where the window or door is in a safety-critical location, the new unit will be toughened or laminated glass.
What should you do straight after a window breaks?
- Keep people and pets away from the window and the area below it, inside and out.
- Do not try to pull loose shards out of the frame. Cracked glass can fall unexpectedly, and toughened glass can break up suddenly.
- If glass has fallen, sweep it up carefully wearing sturdy shoes and gloves, and wrap it before putting it in the bin.
- If the break was caused by a break-in or vandalism, contact the police and note the reference – your insurer may ask for it.
- Take photos of the damage for your records and for any insurance claim.
- Call us. We can talk through whether the opening needs making safe now or can wait for a replacement unit.
Please do not try to remove a broken unit yourself. Sealed units are heavy and sharp, glass can collapse as the beads come out, and anything above ground floor means working at height. We will deal with it.
Can you replace one pane of a double glazed window?
Not on its own. A double glazed unit is two panes bonded to a spacer bar and sealed around the edge, so once one pane breaks, the seal is compromised and the cavity is open. The correct repair is a complete new sealed unit, made to the same overall size and thickness so it fits back into the same frame. The frame, hinges, handles and locks are normally unaffected and stay as they are.
Sometimes only the outer pane is cracked and the window still looks intact from inside. It still needs replacing: water and dirt will get into the cavity, the unit will mist, and the crack can spread with temperature changes.
How we deal with broken double glazing
- Phone call. We ask which window or door it is, how badly it is broken, whether it is secure, the floor level and roughly how big it is.
- Making safe if needed. If the pane is badly broken or the property is not secure, we can board the opening or fit temporary glazing. We cannot promise a set arrival time, but we will tell you honestly when we can get to you.
- Measuring. We measure the unit, check the frame and beads for damage, and confirm whether the location needs safety glass.
- Quote and order. We give a written quote and order the unit. Units are made to measure, so there is usually a wait of a few days to a couple of weeks.
- Fitting. We remove any temporary boarding and the remains of the broken unit, fit the new unit on packers, re-bead, clean up and check the window or door works properly.
If you need the opening made safe urgently, see our emergency glazing and boarding page for what to expect.
Does my replacement need to be safety glass?
In many cases, yes. Approved Document K sets out critical locations where glazing must be safety glass: any glazed panel up to 800 mm from floor level, any glazed door up to 1500 mm from floor level, and side panels within 300 mm of the edge of a door. Replacement units in these places should be toughened or laminated, even if the old unit was not.
| Glass type | How it behaves when broken | Where it is often used |
|---|---|---|
| Toughened (BS EN 12150) | Breaks into small, relatively blunt pieces | Doors, low panes, side panels, patio doors |
| Laminated (BS EN 14449) | Cracks but stays held together on its interlayer | Where security or holding the glass in place matters |
| Annealed (standard float) | Breaks into large, sharp shards | Higher panes outside the critical locations |
Toughened glass usually carries a permanent mark in one corner. If you are not sure what you have, we will check when we measure.
Why do double glazed windows crack?
- ImpactBalls, stones thrown up by mowers or strimmers, birds, accidents during building work, or attempted break-ins.
- Thermal stressUneven heating – for example, part of a pane in sun and part in shade, or a dark object right against the glass – can sometimes crack annealed glass, often starting from the edge.
- Frame movementMissing packers or a frame under strain can put pressure on the edge of a unit.
- Spontaneous breakageToughened glass can occasionally shatter without an obvious cause, which can be linked to tiny inclusions in the glass.
Choosing the replacement glass
A broken unit is a good chance to choose the right glass for that opening. For a bathroom or a front-door side panel, obscure and privacy glass may suit better than clear. A modern low-E unit with argon usually performs better than an older unit. If other units in the same window have misted, it can make sense to replace them at the same visit – our misted double glazing repair page explains how failed units are dealt with. Conservatory side and door panels are covered on our conservatory glass units page.
Broken glass in Liverpool homes
Glass breakages are not tied to one type of street, but some patterns repeat. Glazed panels in uPVC front doors and side panels take knocks in busy family homes. Larger patio and bi-fold glazing is more common in places like Formby and on newer estates. In rented properties across areas such as Wavertree and Birkenhead, landlords and agents often need a broken pane dealt with quickly and cleanly between tenancies or after damage. Wherever you are, we cover glazing repairs in Liverpool and across Merseyside.
What affects the cost of replacing broken glass?
The size and shape of the unit, the glass type (toughened, laminated, obscure, low-E or triple), any Georgian bars, whether boarding or temporary glazing was needed first, access and height, and how many units are being replaced. We quote after measuring, and our double glazing repair cost guide explains the factors in more detail.
If you are claiming on home insurance, check your policy first – your insurer decides what they will cover and may want a written quote, which we provide after measuring.
Broken or cracked double glazing?
Call 07777 659786 and tell us which window or door it is and how bad the damage looks. We will talk you through making it safe and getting a new unit made. You can also use the form – we cover repairs to windows and doors around Liverpool, Sefton, Knowsley, St Helens, Wirral and Widnes.
Frequently asked questions
Can you replace just the broken pane in my double glazing?
No. In a double glazed window both panes are part of one sealed unit, so when one pane breaks the seal is lost and the whole unit needs replacing. The new unit is made to the same size and thickness so it fits straight back into your existing frame, and your hinges, handles and locks stay as they are.
Is a cracked outer pane urgent if the inner pane is fine?
It is not usually an emergency, because the inner pane still keeps the weather out. But the unit is no longer sealed, so moisture and dirt will get into the cavity and it will mist, and the crack can spread. It is best to have it measured and replaced soon rather than left.
Will my insurance pay for broken double glazing?
That depends on your policy and the cause of the breakage, and only your insurer can decide. Many policies cover accidental damage or break-ins, sometimes with an excess. Take photos, keep any police reference if it was a break-in, and ask your insurer what they need. We can provide a written quote after measuring.
How long does it take to get a broken unit replaced?
Replacement units are made to measure after we have measured the opening, which usually takes a few days to a couple of weeks. If the window is badly broken or the house is not secure, we can board it or fit temporary glazing in the meantime, then come back to fit the finished unit.
Does a broken glass door panel have to be replaced with safety glass?
Yes. Any glazed door up to 1500 mm from floor level is a critical location, so the replacement must be toughened or laminated safety glass. The same applies to glazed panels up to 800 mm from the floor and side panels within 300 mm of a door edge.
Why did my toughened glass shatter for no reason?
Toughened glass can occasionally break without any obvious impact. This is sometimes linked to tiny inclusions in the glass, or to damage to the edge during earlier fitting. It is uncommon but does happen. The replacement unit is fitted the same way as any other broken unit.